1. Field of the Invention
This invention relates to devices for splicing optical fibers (hereinafter "splicers") and more particularly to such a splicer which provides improved optical fiber entry, self centering and holding to afford the splicing of and alignment of ends of the optical fibers to be spliced.
2. Description of the Prior Art
The art is becoming replete with devices for splicing optical fibers. In such devices the two fibers to be spliced are centered for the purpose of aligning the ends of the fibers. The optical fiber used in the telecommunications industry is mostly a single mode fiber. This fiber typically contains a 8 um.+-.1 um diameter central glass core through which the optical signal is transmitted. The core is surrounded by a glass cladding which has a diameter of 125 um.+-.3 um. The cladding has a slightly different index of refraction than the core.
There are a number of prior art devices which have been designed to make permanent connections or splices in single mode glass fibers. To function properly and produce a low loss splice, all of these devices must align the core portions of the two fibers being spliced to within approximately 10% of their core diameter or less than 1 um.
Some of the prior art devices have non-conformable "V" grooves or non-conformable rods. The fibers to be end centered and aligned are forced into the groove or between the rods. These devices, examples of which are shown in U.S. Pat. Nos. 4,029,390; 4,274,708 and 4,729,619, function satisfactorily as long as the fibers being spliced have the same diameter.
As described above the nominal cladding diameter of 125 um has a tolerance range whose ends are at 122 um and 128 um. When the cladding diameters of the fibers to be spliced are at the opposite ends of the tolerance range the non-conformable "V" groove type devices have difficulty in providing the required core alignment precision.
Others of the prior art devices have three equally spaced ductile or elastomeric surfaces which create an equilateral triangular cross-sectional channel into which the fibers to be spliced are positioned The fiber ends are located between the three equally spaced surfaces. Usually the midpoint of the channel is where the junction between the ends of the two fibers is located. These devices, examples of which are disclosed in U.S. Pat. Nos. 4,391,487; 4,435,038; and 4,593,971 are better suited to accommodate differences in fiber cladding diameter than the non-conformable devices described above.
U.S. Pat. No. 4,824,197 discloses a stamped lightguide interconnect centering element for splicing. After stamping, that element is folded which may introduce various distortions such as internal stresses and variation in the grain of the material used in the element. That device utilizes the well known three equally spaced contact surfaces to form a fiber centering channel. The fiber clamping surfaces are initially spaced far enough apart to allow fibers to be inserted. When the fiber ends have been inserted and it has been determined that they are in contact the splice element, which is seated in a jacket, is closed by pushing a cap into the jacket. The pushing of the cap requires that the craftsperson operate the handle of an assembly tool which requires either that one hand be removed from the fibers or another craftsperson is available to operate the tool.
U.S. Pat. No. 4,921,323 discloses a splicer developed from memory polymers. After the ends of the fibers are inserted the mass is exposed to a stimulus such as heat which causes the mass to recover its inherent shape.
It is desirable that the splicer be relatively easy to manufacture and assemble. It is also desirable that at least the splice element of the splicer use identical stamped or molded parts which then have mirror image characteristics. The use of such parts ensures uniform clamping of the fiber cladding. It is also further desirable that the splicer clamp both the cladding and buffer of a fiber inserted therein. It is further desirable that the splicer be sold completely assembled. This prevents the possible loss of critical parts by the user of the splicer. It is further desirable that the splicer be relatively easy to use and that the same tool be usable with all of the splicers.
It is still further desirable that each of the two fibers to be spliced can be inserted in each end of the splicer independently of each other and without disturbing a fiber that has already been inserted in the one of the ends. This allows one craftsperson to insert the fibers and also allows one craftsperson to reenter the splicer for the purpose of removing one of the fibers for repair or replacement without disturbing the other fiber.
The independent insertion of the fibers allows the splicer of the present invention to be mounted in panels in relatively high densities. All of the fibers on one side of the panel can be inserted in the associated one of the splicers without disturbing any fibers that may have been inserted on the other side. Those other side fibers, if not already inserted in the splicer panel, can be inserted by the same craftsperson who inserted the fibers in the one side splicers without disturbing those inserted fibers. Alternatively, the insertion of those other side fibers can be left for a later time or even another craftsperson.